1. Field of the Invention
This invention relates to photographic motion picture cameras and, more particularly, to apparatus for permitting viewing of images carried by a motion picture film strip contained within a film cassette having a permanent prismatic reflective element at the exposure/projection station, through the taking lens of the camera.
2. Description of the Prior Art
In recent years, advances of tremendous significance have been made in the photographic arts. Among the most recent have been developments which have virtually eliminated the traditional time delay associated with the processing of motion picture film. These developments have provided systems which permit the photographer to view the results of his work immediately after the exposure process has been completed. Most advantageously, such systems provide a film handling cassette from which the film need never be removed during exposure, developing, projecting and editing procedures. Such systems are described in U.S. Pat. Nos. 3,584,944 issued June 15, 1971 in the name of Gerald H. Cook; 3,597,062 issued Aug. 3, 1971 in the name of Rogers B. Downey; 3,615,127 issued Oct. 26, 1971 in the name of Edwin H. Land; and 3,584,942 issued June 15, 1971 in the name of Rogers B. Downey, all of which are assigned to the assignee of the present invention.
A particularly unique feature of such systems is best described in the above-identified U.S. Pat. No. 3,615,127 to Land wherein there is described a compact motion picture film handling cassette adapted to facilitate film exposure operations when mounted in a camera and film processing and projection operations when mounted in a projector or viewer. Such a cassette is supplied with a strip of unexposed photographic film interconnected between a pair of reels and includes a film exposure/projection station to facilitate exposure and projection operations, and a film processing station. Exposure of the film may be effected during a first advancement of the film from the supply reel to the takeup reel across the exposure/projection station. Processing is then effected as the exposed film is returned through the processing station to the supply reel, and drying and exposure operations of the developed film are effected as it is once again advanced from the supply reel across the exposure/projection station onto the takeup reel.
An especially important feature of such cassette is the fact that a prism is mounted behind the film at the exposure/projection station. The prism is adapted to admit light directed through it by a condenser system in the projector. The projection light is directed into the side of the cassette and reflected by a reflecting surface of the prism through the film and outwardly through projection optics included in the projector. This prism is mounted as a permanent part of the cassette and simplifies the optics and the mechanical features of the projector adapted to receive the cassette. The prism is also responsible for maintaining the effective aperture of the projection optics within a limited space, whereas a mirror-type reflector would significantly reduce the effective aperture within the same space. It also permits the cassette to be introduced simply into a projector without the necessity of introducing optical portions of the projector into the cassette structure or of pulling the film from the cassette to thread it through a projection station.
The above-cited U.S. Pat. No. 3,615,127, points out further that the incorporation of a permanent prismatic element at the exposure/projection station makes it possible to modify a camera adapted to use such a cassette so that it may be used for viewing developed film. More specifically, it points out that by incorporating in the camera a source of light adjacent the entrance of the prismatic element, the camera may be used to view the film directly through the lens of the camera. Such a light source may comprise, for example, a normally closed but openable light collecting lens or window or, alternatively, a built-in examination light for directing light into the prism.
It has been found that such direct viewing through the lens of a camera does not produce a good viewable image and it is towards a satisfactory arrangement wherein film carried by such a multipurpose film cassette may be viewed within a camera that the present invention is directed.